The folks over there at Chimpomatic have written a fairly nice review of The Empyrean:

As a complete record, this is certainly a more focused release than Frusciante's six-albums-in-six-months period, as while each of those records yielded several gems, there was a certain sense of in-cohesiveness, which is clearly absent here. While Frusciante describes The Empyrean as a "concept album", he acknowledges that it may not come accross as narrative in that sense, but there is certainly a running theme within the songs, which all hold the same mood and tone - echoing feelings of loss, death and spirituality. The result is an outstanding, thoroughly involving and innovative album - which provides a sometimes challenging listen, with many rewards.

You can read the whole review on their website. They're also introducing the first-time listeners to John's extended opus in a cheatsheet. In other words, they have picked a pretty good list of songs they're advising people to listen to before they give The Empyrean a try.

On the other side, a music review blog with quite loyal followers, Indie Paws, or precisely Flint, one of their writers, has written a lentghy retrospective of John's career, having given in-depth honest reviews of each album, including biography bits. I recommend it wholeheartedly.
The Career of One John Frusciante - part one
The Career of One John Frusciante - part two

A new digest of reviews will be published sometime tomorrow and, in the meantime, there will be a very special review of The Empyrean written with this site's audience in mind. Stay tuned!